1. Field of the Invention
The present invention relates generally to an MBMS (Multimedia Broadcast/Multicast Service), and in particular, to a paging method to provide an MBMS service.
2. Description of the Related Art
Today's rapid development of communication technology has driven the development of the WCDMA (Wideband Code Division Multiple Access) mobile communication systems to provide, aside from the traditional voice service, packet data service for transmitting a large volume of data such as packet data and circuit data and multimedia broadcasting/communication. To support the multimedia broadcasting/communication, the MBMS is under discussion. The MBMS services multiple UEs (User Equipments) from one or a plurality of multimedia data sources.
The MBMS generically refers to a service of transmitting the same multimedia data to multiple users over a wireless network. The users share one radio channel, thus saving radio resources.
The MBMS supports a multimedia transmission including real-time video and audio, still images, and text. Depending on a multimedia transmission type, the MBMS can simultaneously provide audio and video data, requiring a large volume of transmission resources. Since an MBMS service transmits the same data to a plurality of cells where users are situated in an MBMS service, a point-to-point (PtP) or point-to-multiple (PtM) connection is established according to the number of users within the cells.
FIG. 1 illustrates nodes involved in the provisioning of an MBMS service over a mobile communication network.
Referring to FIG. 1, UEs 161, 162, 163, 171 and 172 (UE 1 to UE 5) are terminal devices or subscribers capable of receiving the MBMS service. Cells 160 and 170 (cell 1 and cell 2) are Node B devices for wirelessly transmitting MBMS data to the subscribers under the control of Node Bs. An RNC (Radio Network Controller) 140 controls the cells 160 and 170, selectively transmits multimedia data to the cells, and controls radio channels established for the provisioning of the MBMS service. The RNC 140 is wirelessly connected to the UEs 161, 162, 163, 171 and 172 via an RRC (Radio Resource Control) interface.
The RNC 140 is connected to a PS (Packet Switched or Packet Service) network such as the Internet through an SGSN (Serving GPRS Support Node) 130. Communications are conducted between the RNC 140 and the PS network by PS signaling. Especially a lu-PS interface is defined between the RNC 140 and the SGSN 130. The SGSN 130 controls the MBMS-related services for the subscribers. The major functions of the SGSN 130 are to manage the service billing data for each subscriber and to selectively transmit the multimedia data to the RNC 140.
A transit network (NW) 120 provides a communication path between a BM-SC (Broadcast Multicast Service Center) 110 and the SGSN 130. The transit NW 120 can be connected to an external network through a GGSN (Gateway GPRS Support Node). The BM-SC 110 is an MBMS data source responsible for MBMS data scheduling.
Meanwhile, the RNC 140 is connected to a CS (Circuit Switched) network through an MSC (Mobile Switching Center) 150. The CS network is a connection-based, voice-oriented legacy communication network. Communications are made between the MSC 150 and the RNC 140 by CS signaling. Especially, a lu-CS interface is defined between the RNC 140 and the MSC 150.
An MBMS data stream is delivered to the UEs 161, 162, 163, 171 and 172 through the transit NW 120, the SGSN 130, the RNC 140, and the cells 160 and 170.
While not shown in FIG. 1, a plurality of SGSNs may be involved in providing one MBMS service and a plurality of RNCs may operate under one SGSN. Each SGSN transmits data selectively to the RNC 140 and the RNC 140 transmits data selectively to a plurality of cells. To that end, lists of destination nodes are stored so that MBMS data can be selectively delivered to the nodes. The lists include an RNC list for an SGSN and a cell list for an RNC.
Context creation precedes the UEs' access to the network and receiving a service from the network. A context is defined as a set of information required for the provisioning of a service between the UEs and a network node. The major contexts are a UE context and an MM (Mobility Management) context.
FIG. 2 is a diagram illustrating a signal flow for providing an MBMS service between a UE and a network. In the illustrated case, a BM-SC 306 communicates with a UE 302 through an RNC 304.
Referring to FIG. 2, the UE 302, which intends to receive the MBMS service, registers with a service provider, the BM-SC 306 in step 310 (Subscription). The Subscription involves the exchanging of basic information associated with the billing and the service reception between the BM-SC 306 and the UE 302.
In step 320, the UE 302 acquires the basic information about the MBMS services (Announcement). For example, the basic information provides the MBMS service IDs (Identifiers) identifying the MBMS services available from the BM-SC 306 and the action times and durations of the MBMS services. An MBMS service ID includes a multicast address and an APN (Access Point Name).
In the Announcement step, the nodes between the BM-SC 306 and the UE 302, that is, the RNC 304, an SGSN, and a transit NW are provided with information related to the UE 302 and nodes connected to the UE 302. For example, the SGSN determines a list of UEs that are to receive the MBMS service and a list of RNCs having the UEs under their control. The SGSN transmits the MBMS data to only the RNCs that require the MBMS data by referring to the lists.
The UE 302 joins a desired MBMS service in step 330 (Joining). For the Joining, the UE 302 transmits to the BM-SC 306 at least one desired MBMS service ID from among the MBMS service IDs acquired in the Announcement step.
In step 340, the UE 302 is paged to be notified that the requested MBMS service will start (Notification). In the Notification step, the group paging occurs to a plurality of UEs that have joined the MBMS service, including the UE 302.
The radio resources are actually allocated between the UE 302 and the RNC 304, for the MBMS service, and information about the radio resource allocation is delivered to the associated nodes in step 350 (Radio Resource Allocation). The RNC 304 can select a PtM transmission mode or a PtP transmission mode according to the number of UEs in each of its underlying cells and its radio resource management (RRM) function.
In step 360, the MBMS data is transmitted to the UE 302 through the RNC 304 (Data Transfer). If a ciphering key for the MBMS service needs to be changed in step 306, the RNC 304 relates a new ciphering key to every UE that is receiving the MBMS service.
Upon termination of the MBMS service, the allocated radio resources are released and the release of the MBMS radio resources is notified to the UE 302 in step 370 (Radio Resource Release). While not shown, the UE 302 itself can request termination of the MBMS service and terminate the MBMS service while the data transfer is ongoing for the MBMS service (i.e. during step 360).
For the provisioning of an MBMS service, a paging message is transmitted to a plurality of UEs which have joined the MBMS service to notify them of the start of a session or the presence of the MBMS control information. To indicate the presence of the paging message, a paging indicator (PI) is transmitted to the UEs. The PI is directed to the plurality of UEs.